Au-Ir alloy nanofibers synthesized from Au-Ir/IrO2 composites via thermal hydrogen treatment: Application for glucose oxidation

Abstract

This paper reports the facile formation of the alloy nanofibers of highly immiscible Au and Ir with diverse composition ratios (denoted as TH2_AuxIr1-x, x= 0.05, 0.10 or 0.33, relative molar content of Au precursor) and the application for direct glucose oxidation. First, the composite nanofibers consisting of Ir/IrO2 fibrous main frames decorated with Au nanoparticles (denoted as Pre_AuxIr1-xOy ) were synthesized via electrospinning and calcination. Then, these composites were annealed under H-2 gas flowing and successfully transformed to AuIr alloy nanofibers along with IrO2 reduction to Ir metal in the Ir/IrO2 fibrous frames. Thermal H-2-treatments with varying temperatures and duration times confirmed that Au-Ir alloy production required an unusually low temperature >= 90 degrees C at which Au and Ir were completely alloyed within 1 min. This study suggests that the Au-Ir alloying and IrO2 reduction occur simultaneously and promote each other. TH2_Au0.33Ir0.67, with similar to 50.4 % Au atomic %, was found to still have segregated Au phase, indicating the limited solubility (molar ratio of Au/Ir < 1). Alloyed TH2_Au0.10Ir0.90 exhibited high electroactivity for glucose oxidation: a surprisingly low onset potential ( < < - 0.4 V vs SCE) and greatly enhanced oxidation current levels compared with Pre_Au0.10Ir0.90Oy and pure Au nanoparticles. The high activity of TH2_Au0.10Ir0.90 go was attributed to the higher surface area of Au and more favorable formation of catalytically active OHads in the Au-Ir alloy. Current study presents that Au-Ir alloys can be formed under moderate condition via thermal H-2-treatment and possess a feasibility for nonenzymatic glucose oxidation.